The invention relates to mechanisms for controlling the movement of a throttle in an internal combustion engine and, more particularly, to engine throttle controls for marine propulsion devices, such as outboard motors and stern drive units.
Marine propulsion devices commonly employ a single lever control including a main control lever which is movable in opposite directions from a netural position to sequentially actuate the clutch and then advance the throttle setting. With this arrangement, the clutch is actuated to either a forward drive or reverse drive position before there is an appreciable advancement of the throttle and the clutch can not be actuated before the throttle is returned to a low speed or idle setting. The main control lever is usually connected to the throttle valve of the engine carburetor via a linkage arrangement, such as a push-pull cable, which is connected to a rotatable or pivotable throttle lever adapted to actuate the throttle valve.
When the push-pull cable is connected directly to the throttle lever, incremental movement of the main control lever from the neutral or idle position can produce a variable amount of throttle lever movement and, thus, unequal throttle setting advancement for the same amount of main control lever movement. Consequently, during portions of the main control lever movement between the idle and full throttle positions, relatively small amounts of control lever movement can produce relatively large advancement of the throttle setting. This condition is particularly undesirable at lower engine speeds when uniform throttle control is usually most needed for boat handling, for example, when easing a boat up to a dock or the like.